#include <stdio.h>
int main(void)
{
	int j,k,s,i,sum=0;
	j=k=i=1;
	scanf("%d",&s);
	while (s){
		k=s%10;
		  if(i%2==1){
			  k=k*j;
			  sum=sum+k;
			  j=j*10;
		  }
		s=s/10;
		i++;
	}
	printf("%d\n",sum);
	return 0;
}